This invention relates to a method for preparing compositions of matter that are useful as catalysts, and to a method of using these catalysts for polymerizing addition polymerizable monomers. More particularly the present invention relates to an improved method for preparing a class of catalysts known as cationic metallocene catalysts using a silylium salt activator.
In U.S. Ser. No. 545,403, filed Jul. 3, 1990, (published in equivalent form Mar. 13, 1991 as EP-A-416,815) there are disclosed certain constrained geometry metal complexes and catalysts derived by reacting the metal complex with activating cocatalysts. In U.S. Pat. No. 5,064,802 (published Mar. 20, 1991 in equivalent form as EP-A-418,044) there are further disclosed certain constrained geometry metal catalysts formed by reacting such metal complexes with salts of Bronsted acids containing a non-coordinating compatible anion. The reference discloses the fact that such complexes are usefully employed as catalysts in addition polymerizations. In U.S. Ser. No. 884,966, filed Mar. 15, 1992, U.S. Pat. No. 5,350,723, an alternative technique for preparing cationic constrained geometry catalysts using carbenium cationic activator compounds is disclosed. For the teachings contained therein, the foregoing United States patent and applications are herein incorporated by reference.
It has been previously known in the art to employ carbenium, oxonium or sulfonium ions to generate cationic Group 4 metallocene catalysts. Such a process is disclosed in EP-A2-426,637 published May 8, 1991.
J. B. Lambert, et al., Organometallics, 13, 2430-2443 (1994), disclosed a process for preparing silylium borate salts by reaction of carbenium borates with silanes. Lewis base adducts of silylium borates, especially ether and acetonitrile adducts of silylium borates, are disclosed in S. R. Bahr, et al., J. Am. Chem. Soc., 115, 4514-4519 (1993) and in M. Kira, et al., J. Am. Chem. Soc., 114, 6697-6700 (1992), respectively. None of the foregoing references discloses a utility for such silylium compounds in the formation of polymerization catalysts.
It would be desirable if there were provided an improved method that would allow the production of even more efficient catalysts as well as an improved addition polymerization process utilizing such catalysts.